The Mars Curiosity laboratory, looking up rather than down, has taken a series of photos of Mars’ moon Phobos as it transited across the face of the Sun in a partial eclipse. The purpose, in addition to the visual appeal, is to map very small changes in the orbit of Phobos, which are effected by the changing shape of Mars. NASA’s Opportunity rover is taking similar photos. The two bodies interact, such that Phobos produces tidal-like forces which change the shape of Mars. From these measurements of Mars’s changing shape, scientists will be able to get a better understanding of its internal structure and composition. They will be able to tell how “soft” Mars is on the inside, Mark Lemmon explained during a teleconference yesterday. There is a time limit to making these observations. Due to the changes on Mars, caused by Phobos, Phobos’s orbit itself is decaying. Phobos is slowing down, and Mars is pulling the tiny moon closer to it, and to an eventual break-up and crash. But Lemmon estimates that may not happen for 10-15 million years.

Otherwise, the rover’s science team has chosen a near-by rock for their first science target, which they dubbed Jacob Matijevic, after the surface operations system chief engineer who planned the traverses of all of the previous Mars rovers. He passed away a few days after Curiosity landed. Although during the teleconference, reporters wanted to know what was unusual about this rock, for it to be chosen for Curiosity’s first up-close encounter, Project Scientist John Grotzinger stressed that it is because they believe it is a common basalt rock that makes it a good target to be used to calibrate Curiosity’s instruments. The chemical composition of Jacob Matijevic will be the focus of the investigations.